1. Field of the Invention
The present invention is directed to a graphite oxide and graphene preparation method, particularly to a graphite oxide and graphene preparation method using plasma electrolytic process.
2. Description of the Prior Art
Graphene is a newly discovered carbon nanomaterial and provided with many excellent properties such as linear spectrum, high electron mobility, the unique optical properties, high elasticity, sturdiness and single atomic width. Therefore, graphene is viewed as a breakthrough nanomaterial for applications in optoelectronics, energy and chemical material fields.
The chemical reduction of exfoliated graphite oxide is widely considered to be the most promising approach for the large-scale production of graphene; this process involves (i) oxidation of graphite to graphite oxide (GO) (ii) exfoliation of GO through ultrasonication or thermal treatment to yield graphene oxide; and (iii) chemical reduction of graphene oxide to a graphitic network of sp2-hybridized carbon atoms.
The mixtures of strong oxidants and concentrated acids used to prepare GO are, however, highly toxic and dangerously unstable, requiring extra safety precautions. Moreover, the discharge of large quantities of acidic waste poses an environmental risk.
Paulmier et al. (Thin Solid Films 515(5):pp. 2926-2934) taught deposition of nano-crystalline graphite films on titanium substrate with atmospheric pressure plasma deposition method from a predominantly ethanol liquid phase by plasma electrolysis. Paulmier used graphite (anode was composed of graphite) as anode although Paulmier formed graphite films by plasma electrolysis. Richenderfer et al. taught a plasma-assisted electrochemical approach for exfoliating pristine graphite in an acidic electrolyte with surfactant to graphene. Richenderfer used graphite as anode and used micro-plasma as the cathode rather than a traditional physical cathode, such as platinum so as to enhance the electric field. In addition, Richenderfer used acidic electrolyte (containing HCl) along with a surfactant in terms of an electrochemical method that in needs of concentrated acid for reaction. Hence, acidic waste manipulation in Richenderferes method is required and leaves room for improvement. Furthermore, the micro-plasma generating cathode with Argon gas indicates the requirement of special apparatus as well as complicated manipulation.
Thus, a new method for the preparation of GO without the need for toxic chemical agents or the harsh oxidation of graphite would be of great interest from the perspectives of both science and technology and environmental protection. This method can also be used to produce graphene sheets directly from graphite cathode providing the anode and the concentration of the basic electrolyte are properly chosen.